Catheter balloon having impregnated balloon skirt sections

ABSTRACT

A balloon catheter and a method of making a balloon catheter, having a balloon with a first layer and a second layer, the first layer having at least one impregnated section impregnated with a polymeric material compatible with a polymeric material forming the catheter shaft. At least a portion of the impregnated section is fusion bonded to the shaft. In a presently preferred embodiment, the impregnated section is adjacent to a section of the first layer which is not impregnated with the compatible polymeric material. The impregnated section provides improved bonding of the balloon to the catheter shaft while minimizing the effect of the bond on catheter performance characteristics such as profile and flexibility.

BACKGROUND OF THE INVENTION

This invention generally relates to medical devices, and particularly tointracorporeal devices for therapeutic or diagnostic uses, such asballoon catheters. In percutaneous transluminal coronary angioplasty(PTCA) procedures, a guiding catheter is advanced until the distal tipof the guiding catheter is seated in the ostium of a desired coronaryartery. A guidewire, positioned within an inner lumen of a dilatationcatheter, is first advanced out of the distal end of the guidingcatheter into the patient's coronary artery until the distal end of theguidewire crosses a lesion to be dilated. Then the dilatation catheterhaving an inflatable balloon on the distal portion thereof is advancedinto the patient's coronary anatomy, over the previously introducedguidewire, until the balloon of the dilatation catheter is properlypositioned across the lesion. Once properly positioned, the dilatationballoon is inflated with fluid one or more times to a predetermined sizeat relatively high pressures (e.g. greater than 8 atmospheres) so thatthe stenosis is compressed against the arterial wall and the wallexpanded to open up the passageway. Generally, the inflated diameter ofthe balloon is approximately the same diameter as the native diameter ofthe body lumen being dilated so as to complete the dilatation but notoverexpand the artery wall. Substantial, uncontrolled expansion of theballoon against the vessel wall can cause trauma to the vessel wall.After the balloon is finally deflated, blood flow resumes through thedilated artery and the dilatation catheter can be removed therefrom.

In such angioplasty procedures, there may be restenosis of the artery,i.e. reformation of the arterial blockage, which necessitates eitheranother angioplasty procedure, or some other method of repairing orstrengthening the dilated area. To reduce the restenosis rate and tostrengthen the dilated area, physicians frequently implant a stentinside the artery at the site of the lesion. Stents may also be used torepair vessels having an intimal flap or dissection or to generallystrengthen a weakened section of a vessel. Stents are usually deliveredto a desired location within a coronary artery in a contracted conditionon a balloon of a catheter which is similar in many respects to aballoon angioplasty catheter, and expanded to a larger diameter byexpansion of the balloon. The balloon is deflated to remove the catheterand the stent left in place within the artery at the site of the dilatedlesion. Stent covers on an inner or an outer surface of the stent havebeen used in, for example, the treatment of pseudo-aneurysms andperforated arteries, and to prevent prolapse of plaque. Similarly,vascular grafts comprising cylindrical tubes made from tissue orsynthetic materials such as polyester, expanded polytetrafluoroethylene,and DACRON may be implanted in vessels to strengthen or repair thevessel, or used in an anastomosis procedure to connect vessels segmentstogether.

In the design of catheter balloons, characteristics such as strength,compliance, and profile of the balloon are carefully tailored dependingon the desired use of the balloon catheter, and the balloon material andmanufacturing procedure are chosen to provide the desired ballooncharacteristics. A variety of polymeric materials are conventionallyused in catheter balloons. Use of polymeric materials such as PET thatdo not stretch appreciably consequently necessitates that the balloon isformed by blow molding, and the deflated balloon material is foldedaround the catheter shaft in the form of wings, prior to inflation inthe patient's body lumen. However, it can be desirable to employballoons, referred to as formed-in-place balloons, that are not foldedprior to inflation, but which are instead expanded to the workingdiameter within the patient's body lumen from a generally cylindrical ortubular shape (i.e., essentially no wings) that conforms to the cathetershaft.

A catheter balloon formed of expanded polytetrafluoroethylene (ePTFE)has been suggested. ePTFE is PTFE which has been expanded to form porousePTFE which typically has a node and fibril microstructure comprisingnodes interconnected by fibrils. However, ePTFE has proven difficult tobond to balloon liner materials and/or to catheter shafts. Onedifficulty has been bonding ePTFE absent the use of adhesives which canincrease stiffness at the bond site, and/or bonding pretreatments whichcan cause decomposition of the ePTFE fibril structure.

It would be a significant advance to provide a catheter balloon, orother medical device component, with improved performance andbondability.

SUMMARY OF THE INVENTION

This invention is directed to a balloon catheter and a method of makinga balloon catheter, having a balloon with a first layer and a secondlayer, the first layer having at least one impregnated sectionimpregnated with a polymeric material compatible with a polymericmaterial forming the catheter shaft. At least a portion of theimpregnated section is fusion bonded to the shaft. In a presentlypreferred embodiment, the impregnated section is adjacent to a sectionof the first layer which is not impregnated with the compatiblepolymeric material. The impregnated section provides improved bonding ofthe balloon to the catheter shaft while minimizing the effect of thebond on catheter performance characteristics such as profile andflexibility.

A balloon catheter of the invention generally comprises an elongatedshaft having a proximal end, a distal end, at least one lumen, and atleast a surface formed of a polymeric material, and a balloon on adistal shaft section with an interior in fluid communication with the atleast one lumen of the shaft. The balloon has a proximal skirt sectionbonded to the shaft, a distal skirt section bonded to the shaft, andfirst and second layers extending from the proximal skirt section to thedistal skirt section. At least one of the skirt sections of the balloonis formed at least in part by the impregnated section of the first layerfusion bonded to the shaft. In a presently preferred embodiment, thefirst layer has a proximal impregnated section at least in part formingthe proximal skirt section, and a distal impregnated section at least inpart forming the distal skirt section. Preferably, end sections of thesecond layer are also bonded to the shaft, although they are notimpregnated. Thus, the proximal and distal skirt sections of the balloonare preferably formed in part by the end sections of the second layer,and in part by the impregnated sections of the first layer of theballoon. The proximal and distal impregnated sections of the first layerare preferably adjacent to one or more sections of the first layer whichare not impregnated with the polymeric material impregnated in theimpregnated sections.

The impregnated section of the first layer of the balloon is impregnatedwith a polymeric material which is compatible with the polymericmaterial of the shaft, so that the impregnated section improves fusionbonding between the first layer of the balloon and the shaft. In oneembodiment, the bond between the shaft and the proximal and distal skirtsections of the balloon is sufficiently strong to withstand ballooninflation pressures of about 90 to about 300 psi without failing (i.e.,without rupturing or ballooning at the site of the bond or allowinginflation fluid to seep through the ePTFE layer of the balloon). Theterm compatible should be understood to refer to polymeric materialswhich are fusion bondable together. More specifically, compatiblepolymeric materials bond together by chemical bonds (i.e., covalent orhydrogen bonds), and preferably are thermodynamically miscible together.In one embodiment, the polymeric material impregnated in the first layerimpregnated section (“the compatible polymeric material”) is the samepolymeric material as the shaft polymeric material. For example, in oneembodiment, the compatible polymeric material and the shaft polymericmaterial are the same polymer and are selected from the group consistingof Nylon 12, polyether block amide (PEBAX), polyurethanes, andcopolymers thereof, and acrylonitrile butadiene styrene (ABS). However,the compatible polymeric material is not necessarily the same polymer asthe shaft polymeric material. In one embodiment, the compatiblepolymeric material is from the same family or class of polymericmaterials as the shaft polymeric material, so that the polymers willcovalently bond together. For example, in one embodiment, the compatiblepolymeric material is a nylon and the shaft polymeric material is PEBAX,and thus the polymers are both from the family of polymers known aspolyamides. In another embodiment, the compatible polymeric material andthe shaft polymeric material are from different polymer families, butwill hydrogen bond together, such as, for example, polyurethane andPEBAX, or nylon and polyurethane.

In one embodiment, the compatible polymeric material is soluble in analcohol, unlike polymers such as nylon 12 which are not soluble inalcohol. For example, ELVAMIDE, available from Dupont, is athermoplastic polyamide soluble in alcohols including methanol, ethanol,2-propanol, and a mixture of these with water. Such alcohols are readilyavailable, and typically have a higher vapor pressure, lower toxicity,and lower cost than organic solvents commonly used for polymers such asnylon 12, and thus improve the manufacturability of the ballooncatheter.

Preferably, the one or more impregnated sections of the balloon firstlayer are located only at the regions of the balloon skirt sections.Thus, the impregnated sections typically have a shorter length than thelength of the first layer which is not impregnated with the compatiblepolymeric material. The combined length of the proximal and distalimpregnated sections of first layer is typically about 10 to about 50%of the length of the first layer. In one embodiment, the impregnatedsection(s) of the first layer has a length approximately equal to thelength of the section(s) of the first layer bonded to the shaft.Consequently, the impregnated section(s) has minimal effect on balloonperformance characteristics such as compliance.

The first layer is formed of a porous polymeric material which in oneembodiment is selected from the group consisting of expandedpolytetrafluoroethylene (ePTFE), an expanded ultra high molecular weightpolyolefin such as expanded ultra high molecular weight polyethylene,porous polyethylene, porous polypropylene, and porous polyurethane. Inone embodiment, the porous material has a node and fibrilmicrostructure. The node and fibril microstructure, when present, isproduced in the material using conventional methods. ePTFE and expandedultra high molecular weight polyethylene typically have a node andfibril microstructure, and are not melt extrudable. However, a varietyof suitable polymeric materials can be used in the method of theinvention including conventional catheter balloon materials which aremelt extrudable. Preferably, ePTFE is formed into a balloon layer bybonding wrapped layers of the polymeric material together to form atubular member, and not by conventional balloon blow molding. Althoughdiscussed primarily in terms of the embodiment in which the first layerof the balloon comprises ePTFE, it should be understood that a varietyof suitable polymers may be used for the first layer.

In a presently preferred embodiment, the first layer is an outer layerrelative to the second layer, although the first layer may alternativelybe an inner layer relative to the second layer. In one embodiment, theouter (e.g., first) layer extends beyond the ends of the inner (e.g.,second) layer. Specifically, in one embodiment, the first layer has aproximal end section and a distal end section, extending beyond theinner layer and in contact with and bonded to the shaft. The impregnatedsections of the outer layer extend along at least part of the endsections of the outer layer which are in contact with and bonded to theshaft. Although discussed primarily in terms of the embodiment in whichthe first layer formed of ePTFE or other porous polymer is the outerlayer of the balloon, it should be understood that the balloon can haveone or more ePTFE layers forming an outer, inner, or middle layer of theballoon.

A balloon catheter of the invention can be configured for use in avariety of applications including coronary and peripheral dilatation,stent delivery, drug delivery, and the like.

A method of making a balloon catheter which embodies features of theinvention generally includes positioning a distal section of a cathetershaft within a first tube forming a tubular inner layer of the balloon,the tubular inner layer being formed of an elastomeric polymer andhaving a proximal end section, and a distal end section. A second tubeforming a tubular outer layer of the balloon, formed of a porouspolymeric material, is positioned on an outer surface of the tubularinner layer, with a proximal end section and a distal end section of thetubular outer layer in contact with the catheter shaft and having atleast a portion impregnated with a polymeric material compatible withthe polymeric material of the shaft and adjacent to a section of theouter layer which is not impregnated with the compatible polymericmaterial. The inner tubular layer is preferably bonded to the shaftbefore the outer tubular layer is positioned therearound, although itmay alternatively be bonded to the shaft during the fusion bonding ofthe outer layer to the shaft. Thus, in one embodiment, prior topositioning the outer layer around the inner layer, heat is applied atthe proximal and distal end sections of the inner tubular layer, to meltthe shaft polymeric material and the polymeric material of the innertubular layer and fusion bond the proximal and distal end sections tothe catheter shaft. Then the outer tubular layer is positionedtherearound and heat similarly applied thereto to melt the shaftpolymeric material and the compatible polymeric material and fusion bondthe proximal and distal end sections to the catheter shaft.

Although discussed in terms of a preferred embodiment in which thefusion bond between the balloon and shaft is a heat fusion bond, thefusion bond may alternatively be a solvent fusion bond. In the heatfusion bonding, the polymeric materials are heated to an elevatedtemperature at or around the melting temperature(s) of the polymericmaterials, so that the polymers melt together. The elevated temperatureis typically within about 120° C. to about 250° C. of the meltingtemperature of the polymers. For example, in one preferred embodiment,the elevated temperature is about 170° C. or more for PEBAX, and about120° C. or more for polyurethane. Alternatively, the polymeric materialsare solvent fusion bonded together by solubilizing the polymers togetherin a solvent and evaporating the solvent.

The balloon catheter of the invention has an improved bond between theballoon and the catheter shaft due to the impregnated section of thefirst layer of the balloon. The impregnated section provides a strongfusion bond, without requiring adhesives or polymer sleeves, and thusminimizes disadvantageously large increases in stiffness and profile atthe bond. Moreover, the balloon of the invention has a improvedmanufacturability. These and other advantages of the invention willbecome more apparent from the following detailed description andaccompanying exemplary figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view, partially in section, of a stent deliveryballoon catheter embodying features of the invention.

FIG. 1A is an enlarged sectional view of the catheter shown in FIG. 1,taken within area 1A.

FIG. 2 is a transverse cross sectional view of the balloon cathetershown in FIG. 1, taken along line 2—2.

FIG. 3 is a transverse cross sectional view of the balloon cathetershown in FIG. 1, taken along line 3—3.

FIG. 4 is a transverse cross sectional view of the balloon cathetershown in FIG. 1, taken along line 4—4.

FIG. 5 illustrates the balloon catheter of FIG. 1, with the balloon inan inflated configuration to expand the stent within the patient's bodylumen.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an over-the-wire type stent delivery balloon catheter10 embodying features of the invention. Catheter 10 generally comprisesan elongated catheter shaft 12 having an outer tubular member 14 and aninner tubular member 16. Inner tubular member 16 defines a guidewirelumen 18 configured to slidingly receive a guidewire 20, and the coaxialrelationship between outer tubular member 14 and inner tubular member 16defines annular inflation lumen 22, as best shown in FIG. 2 illustratinga transverse cross section of the distal end of the catheter shown inFIG. 1, taken along line 2—2. An inflatable balloon 24 disposed on adistal section of catheter shaft 12 has a proximal skirt section 25sealingly secured to the distal end of outer tubular member 14 and adistal skirt section 26 sealingly secured to the distal end of innertubular member 16, so that the balloon interior is in fluidcommunication with inflation lumen 22. An adapter 36 at the proximal endof catheter shaft 12 is configured to provide access to guidewire lumen18, and to direct inflation fluid through arm 38 into inflation lumen22. In the embodiment illustrated in FIG. 1, the balloon 24 isillustrated in a noninflated configuration, with an expandable stent 30mounted on the working length of the uninflated balloon 24 for deliveryand deployment within a patient's body lumen 32. In the embodimentillustrated in FIG. 1, the uninflated balloon 24 has a wingless, lowprofile configuration prior to complete inflation of the balloon. Thedistal end of catheter may be advanced to a desired region of thepatient's body lumen 32 in a conventional manner, the balloon 24inflated to expand stent 30, and the balloon deflated, to implant thestent 30 in the body lumen 32.

Balloon 24 has an outer layer 33 and an inner layer 34, extending fromthe proximal skirt section 25 to the distal skirt section 26 of theballoon. In the embodiment illustrated in FIG. 1, the outer layer 33 ofthe balloon 24 has a proximal impregnated section 27 bonded to the outertubular member 14, and a distal impregnated section 28 bonded to theinner tubular member 16. The impregnated sections 27, 28 of the outerlayer 33, together with end sections of the inner layer 34 bonded to theshaft 12, form the proximal and distal skirt sections 25, 26,respectively. Thus, in the embodiment illustrated in FIG. 1, theproximal skirt section 25 is formed at least in part by a proximal endsection of the inner layer 34 which is bonded to the shaft outer tubularmember 14 and by the proximal impregnated section 27 of the outer layer33 which extends beyond the inner layer 34 and which is bonded to theshaft outer tubular member 14. Similarly, the distal skirt section 26 isformed at least in part by a distal end section of the inner layer 34which is bonded to the shaft inner tubular member 16 and by the distalimpregnated section 28 of the outer layer 33 which extends beyond theinner layer 34 and which is bonded to the shaft inner tubular member 16.

The length of the sections of each layer 33 and 34 of the balloon 24secured to the shaft to form the proximal and distal skirt sections 25,26 are preferably minimized. Thus, the proximal and distal skirtsections 25,26 preferably have a length about equal to the minimallength required to provide a suitably strong bond between the balloon 24and the shaft 12. The length of the proximal end section of the innerlayer 34 bonded to the outer tubular member 14 is about 1 to about 5 mm,and the length of the proximal end section of the outer layer 33extending beyond the inner layer 34 and bonded to the outer tubularmember 14 is typically about 1 mm to about 4 mm, preferably about 1 mmto about 2 mm. Similarly, length of the distal end section of the innerlayer 34 bonded to the inner tubular member 16 is about 1 to about 5 mm,and the length of the distal end section of the outer layer 33 extendingbeyond the inner layer 34 and bonded to the inner tubular member 16 istypically about 1 mm to about 4 mm, preferably about 1 mm to about 2 mm.

The impregnated sections 27, 28 of the outer layer 33 of the balloon 24are impregnated with a polymeric material 40 compatible with thepolymeric material of the outer and inner tubular members 14, 16.Although the distal impregnated section 28 is impregnated with the samepolymer 40 as the proximal impregnated section 27 in the embodiment ofFIG. 1, in an alternative embodiment (not shown), the distal impregnatedsection 28 is impregnated with a different polymer than the polymer 40impregnated in the proximal impregnated section 27. In the embodimentillustrated in FIG. 1, the outer and inner tubular members 14, 16 areeach formed of a single-layered, uniform polymeric member. However, itshould be understood that in alternative embodiments, one or both of theouter and inner tubular members 14, 16 may be a multilayered or blendedpolymeric member. The compatible polymeric material 40 is notnecessarily compatible with all the polymers forming parts of the shaft.Thus, the shaft has at least a surface formed of a polymeric material,and the compatible polymeric material 40 is compatible with saidpolymeric material forming the surface of the outer and inner tubularmembers 14,16 to which the impregnated section is bonded.

The compatible polymer 40 impregnated in sections 27,28 of outer layer33 facilitates fusion bonding the outer layer 33 of the balloon 24 tothe shaft 12. In one embodiment, the compatible polymer 40 is the samepolymer as the polymeric material of the shaft 12, for superior fusionbonding, and is selected from the group consisting of nylon, PEBAX, andpolyurethanes. In another embodiment, the compatible polymeric materialand the shaft polymeric from the same polymer family, and are selectedfrom the group consisting of polyamides (e.g., nylon 12, PEBAX, andElvamide), and polyurethanes (e.g., Pellethane and Tecothane). Thecompatible polymeric material 40 may be the same polymer as, or adifferent polymer than, the polymeric material forming the inner layer34 of the balloon. In a presently preferred embodiment, the inner layeris formed of a polymeric material compatible with the polymeric materialof the shaft 12, to facilitate fusion bonding of layer 34 to the shaft12.

Preferably, the outer layer 33 and inner layer 34 of the balloon 24 arefusion bonded directly to the outer tubular member 14 and the innertubular member 16 of the shaft 12, without an adhesive or separatepolymer layer between the layers 33, 34 and the shaft 12. Alternatively,in one embodiment, an adhesive or a separate polymer member is used tofacilitate bonding at least the inner layer 34 to the shaft 12.Conventional adhesives such as light-cured (e.g., Dymax 204) andcyanoacrylates (e.g., Loctite 4011) may be used to bond inner layer 34to the shaft 12. It should be understood that the surface of outer layer33 in contact with and directly fusion bonded to the shaft 12 may havebeen provided with surface treatments or other pretreatments, forenhancing the bondability of materials such as ePTFE.

In the embodiment illustrated in FIG. 1, the impregnated sections 27, 28extend only along the portions of the outer layer 33 which are incontact with and directly bonded to the shaft. Thus, the distal end ofthe proximal impregnated section 27 is located at the proximal end ofthe inner layer 34, and the proximal end of the distal impregnatedsection 28 is located at the distal end of the inner layer 34. In analternative embodiment (not shown), the distal end of the proximalimpregnated section 27 is located distal to the portion of the outerlayer 33 in contact with and directly fusion bonded to the outer tubularmember 14, and the proximal end of the distal impregnated section 28 islocated proximal to the portion of the outer layer 33 in contact with andirectly fusion bonded to the inner tubular member 16. Preferably, theimpregnated sections 27, 28 of the outer layer 33 of the balloon 24 donot extend into a portion of the outer layer 33 located between theproximal and distal skirt sections 25, 26 of the balloon.

The impregnated sections 27, 28 of the outer layer 33 are adjacent to asection of the outer layer 33 which is not impregnated with thecompatible polymer 40. Thus, the impregnated sections 27, 28 of theouter layer 33 do not extend the entire length of the outer layer 33,and preferably have a combined length which is less than the length ofthe section of the first layer which is not impregnated with thecompatible polymeric material 40. The section of the outer layer 33which is not impregnated with the compatible polymer 40 includes thecentral working length of the balloon 24 on which the stent 30 ismounted. In the embodiment illustrated in FIG. 1, the central section ofthe outer layer 33 is not impregnated with the compatible polymer 40 orwith another polymer, apart from being bonded to inner layer 34 whichmay at least partially fill some of the pores of the porous outer layer33. However, it should be understood that all or part of the sections ofthe outer layer 33 which are not impregnated with compatible polymer 40may be impregnated with a polymeric material different than thecompatible polymer 40.

The length of the proximal impregnated section 27 of outer layer 33 istypically about 5 to about 20%, preferably about 5 to about 15% of thelength of the outer layer 33, and the length of the distal impregnatedsection 28 of outer layer 33 is typically about 5 to about 20%,preferably about 5 to about 15% of the length of the outer layer 33.Specifically, in one embodiment, the length of the proximal impregnatedsection 27 of outer layer 33 is about 1 to about 4 mm, and the length ofthe distal impregnated section 28 of outer layer 33 is about 1 to about4 mm, for a balloon 24 having a length of about 8 to about 60 mm and anominal outer diameter of about 2 to about 18 mm.

In a presently preferred embodiment, the outer layer 33 comprises aporous polymeric material, and preferably a microporous polymericmaterial having a node and fibril microstructure, such as ePTFE, and theinner layer 34 is formed of a polymeric material preferably differentfrom the polymeric material of the outer layer 33. Preferably, thelength of outer layer 33 in contact with inner layer 34 is bondedthereto, and preferably by heat fusion bonding. Inner layer 34 limits orprevents leakage of inflation fluid through the microporous ePTFE toallow for inflation of the balloon 24, and is preferably an elastomericmaterial to facilitate deflation of the balloon 24 to a low profiledeflated configuration. The elastomeric material forming layer 34 mayconsist of a separate layer which neither fills the pores nor disturbsthe node and fibril structure of the ePTFE layer 33, or it may at leastpartially fill the pores of the ePTFE layer 33. The inner layer 34 ispreferably formed of an elastomeric material, including dienes,polyurethanes, silicone rubbers, polyamide block copolymers, and thelike.

The ePTFE layer 33 is formed according to conventional methods, in whicha sheet of ePTFE polymeric material is wrapped with overlapping orabutting edges to form a tubular body and then heated to fuse thewrapped material together. The sheet of polymeric material preferablyhas the desired microstructure (e.g., porous and/or node and fibril)before being wrapped on the mandrel. The sheet of ePTFE polymericmaterial is wrapped spirally along a length of the mandrel, or byfolding the sheet around the circumference of the mandrel so that thelongitudinal edges of the sheet extend in a substantially straight linealong the length of the mandrel, to form one or more layers, andpreferably about two to about five layers, of wrapped material. Themultiple layers of ePTFE are typically heated to fuse the layerstogether. The tube of ePTFE polymeric material is typically furtherprocessed by being stretched, sintered, compacted, and sintered again,to provide the desired properties such as the desired dimension, anddimensional stability (i.e., to minimize changes in length occurringduring inflation of the balloon). The completed ePTFE layer 33 is thenbonded to or otherwise combined with elastomeric liner 34 which in oneembodiment is already secured to the catheter shaft 12.

In a method of making a balloon catheter having a balloon with an innerlayer and an outer layer, a distal section of catheter shaft ispositioned within a tubular inner layer 34 of the balloon, so that thedistal end of the outer tubular member 14 and the distal end of theinner tubular member 16 of shaft 12 are within the proximal and distalend sections of the inner layer 34, respectively. Heat is applied at theproximal and distal end sections of the inner tubular layer 34, to meltthe polymeric material of the shaft 12 and the polymeric material of theinner tubular layer 34 at least at the interface thereof, and fusionbond the proximal and distal end sections of the inner tubular layer 34of the balloon 24 to the outer and inner tubular members 14, 16,respectively. Specifically, in one embodiment, an inner tubular layer 34formed of polyurethanes (e.g., Pursil, and Tecoflex) or dienes such assynthetic diene rubber, and a shaft having at least an outer layerformed of polyamides or polyurethanes, with shrink tubing therearound,are heated by a laser to a temperature at or above the meltingtemperature of the polymers, and specifically to a temperature of about120 to about 250° C., and more specifically to a temperature of greaterthan or equal to about 120° C. for a polyurethane shaft and to atemperature of greater than or equal to about 170° C. for a PEBAX shaft.

A tubular outer layer 33 of the balloon 24, formed of a porous polymericmaterial such as for example ePTFE, is positioned on an outer surface ofthe tubular inner layer 34, with aproximal impregnated section 27 of thetubular outer layer located proximal to the proximal end section of thetubular inner layer 34 and in contact with the outer tubular member 14,and with a distal impregnated section 28 of the tubular outer layer 33located distal to the distal end section of the tubular inner layer 34and in contact with the inner tubular member 16.

The proximal and the distal impregnated end sections 27, 28 of thetubular outer layer 33 of the balloon are impregnated with a polymericmaterial compatible with the polymeric material of the shaft 12.Specifically, a solution of the compatible polymeric material is appliedto the end sections of the outer layer 33 before or after the tubularouter layer 33 is positioned around the balloon inner layer 34 and thecatheter shaft 12. In one embodiment, with the outer layer in placearound the inner layer of the balloon, compatible polymer solution isapplied, as for example by dipping, pouring, or spraying, on an outersurface of the end sections of the outer layer, so that the solutionfills the pores of the porous polymeric material at the end sections ofouter layer 33. Alternatively, the end sections of the outer layer 33 ofthe balloon 24 are impregnated with the compatible polymeric materialsolution before being placed in position around the balloon inner layer34 and the shaft 12, as for example, by dipping the end sections of theouter layer 33 into the solution. A sufficient amount of solution isapplied to saturate the end sections of the outer layer of the balloon,so that the solution fills the pores of the porous outer layer 33 and atleast some compatible polymer is at the inner surface of the outer layerafter evaporation of the solvent. In one embodiment, the amount ofsolution in the porous outer layer 33 is about 1 to about 20% by weight,for a porous outer layer 33 having a porosity prior to impregnation ofabout 80% to about 90%. In one embodiment, after impregnation, theporosity is about 65% to about 75%. The concentration of the compatiblepolymeric material solution is about 5 to about 40%, and preferablyabout 5 to about 15%, depending on the compatible polymer and the natureof the polymer forming the outer layer. In the embodiment in which thecompatible polymeric material solution comprises a common solvent suchas an alcohol such as methanol or ethanol, the concentration of thecompatible polymeric material solution is about 5 to about 40%, andpreferably about 5 to about 15%. After evaporation of the solvent, theamount of compatible polymer impregnated in the outer layer 33 istypically about 1 to about 20% by weight, preferably about 1 to about10% by weight of the outer layer 33.

The proximal and distal impregnated sections 27, 28 of the tubular outerlayer 33 of the balloon 24 are adjacent to one or more sections of theouter layer 33 which are not impregnated with the compatible polymericmaterial. The compatible polymer solution is prevented or inhibited frommigrating beyond the end sections of the outer layer of the balloon andinto the adjacent sections of the outer layer of the balloon by a methodinvolving masking the areas. In one embodiment, at least the majority ofthe compatible polymer solution remains where applied at the endsections of the outer layer 33. In one embodiment, some of the solutionmay migrate beyond the end sections of the outer layer of the ballooninto the adjacent sections of the outer layer 33.

The proximal and distal impregnated sections 27, 28 of the tubular outerlayer 33 of the balloon 24 are heated as set forth above, to melt theshaft polymeric material 12 and the compatible polymeric material 40impregnated in the outer layer 33, and thereby fusion bond the proximaland distal end sections of the outer layer 33 to the catheter shaft 12.Specifically, the shaft and the impregnated section of an outer tubularlayer formed of ePTFE impregnated with a polymer such as for examplepolyamides (e.g., Elvamide) and polyurethanes (e.g., Pellethane andTecothane), with shrink tubing therearound, are heated by a laser, to atemperature at or above the melting temperature of the polymers, andspecifically to a temperature of about 120° C. to about 250° C., tofusion bond the outer layer of the balloon to the shaft.

The resulting balloon catheter preferably has a rupture pressure of atleast about 20 atm. During a medical procedure, the balloon is typicallyinflated to a working pressure of about 6 atm to about 25 atm,preferably about 6 atm to about 20 atm. The balloon is inflatable withinthe working pressure range without the skirt sections 25, 26 of theballoon 24 failing.

The dimensions of catheter 10 are determined largely by the size of theballoon and guidewire to be employed, the catheter type, and the size ofthe artery or other body lumen through which the catheter must pass orthe size of the stent being delivered. Typically, the outer tubularmember 14 has an outer diameter of about 0.025 to about 0.04 inch (0.064to 0.10 cm), usually about 0.037 inch (0.094 cm), and the wall thicknessof the outer tubular member 14 can vary from about 0.002 to about 0.008inch (0.0051 to 0.02 cm), typically about 0.003 to 0.005 inch (0.0076 to0.013 cm). The inner tubular member 16 typically has an inner diameterof about 0.01 to about 0.018 inch (0.025 to 0.046 cm), usually about0.016 inch (0.04 cm), and a wall thickness of about 0.004 to about 0.008inch (0.01 to 0.02 cm). The overall length of the catheter 10 may rangefrom about 100 to about 150 cm, and is typically about 143 cm.Preferably, balloon 24 has a length about 0.5 cm to about 6 cm, and aninflated working diameter of about 2 to about 10 mm.

Inner tubular member 16 and outer tubular member 14 can be formed byconventional techniques, for example by extruding and necking materialsalready found useful in intravascular catheters such a polyethylene,polyvinyl chloride, polyesters, polyamides, polyimides, polyurethanes,and composite materials. The various components may be joined usingconventional bonding methods such as by fusion bonding or use ofadhesives. Although the shaft is illustrated as having an inner andouter tubular member, a variety of suitable shaft configurations may beused including a dual lumen extruded shaft having a side-by-side lumensextruded therein. Similarly, although the embodiment illustrated in FIG.1 is an over-the-wire stent delivery catheter, balloons of thisinvention may also be used with other types of intravascular catheters,such as rapid exchange dilatation catheters. Rapid exchange cathetersgenerally comprise a distal guidewire port in a distal end of thecatheter, a proximal guidewire port in a distal shaft section distal ofthe proximal end of the shaft and typically spaced a substantialdistance from the proximal end of the catheter, and a short guidewirelumen extending between the proximal and distal guidewire ports in thedistal section of the catheter.

While the present invention is described herein in terms of certainpreferred embodiments, those skilled in the art will recognize thatvarious modifications and improvements may be made to the inventionwithout departing from the scope thereof. Moreover, although individualfeatures of one embodiment of the invention may be discussed herein orshown in the drawings of the one embodiment and not in otherembodiments, it should be apparent that individual features of oneembodiment may be combined with one or more features of anotherembodiment or features from a plurality of embodiments.

1. A balloon catheter, comprising: a) an elongated shaft having aproximal end, a distal end, an inflation lumen, and at least a surfaceformed of a polymeric material; and b) a balloon on a distal shaftsection, having an inflatable section with an interior in fluidcommunication with the inflation lumen of the shaft, and having aproximal and a distal skirt section bonded to the shaft, and a first anda second layer extending from the proximal skirt section to the distalskirt section along the entire length of the inflatable section of theballoon, the first layer being a porous polymeric material, and thefirst layer having at least one impregnated section along which pores ofthe porous polymeric material are impregnated with a polymeric materialcompatible with the polymeric material of the shaft and different from apolymeric material forming the second layer of the balloon, theimpregnated section being longitudinally adjacent to a section of thefirst layer which is not impregnated with the compatible polymericmaterial, and at least a portion of the impregnated section being bondedto the shaft.
 2. The balloon catheter of claim 1 wherein the first layerof the balloon is an outer layer relative to the second layer of theballoon.
 3. The balloon catheter of claim 1 wherein the balloon proximalskirt section is formed in part by a proximal end section of the secondlayer of the balloon bonded to the shaft.
 4. The balloon catheter ofclaim 3 wherein the at least one impregnated section of the first layerof the balloon is a proximal impregnated section having at least aportion which is located proximal to the proximal end section of thesecond layer of the balloon and which is fusion bonded to the shaft. 5.The balloon catheter of claim 4 wherein the balloon distal skirt sectionis formed in part by a distal end section of the second layer of theballoon bonded to the shaft, and the first layer of the balloon has adistal impregnated section having at least a portion which is locateddistal to the distal end section of the second layer and which is fusionbonded to the shaft.
 6. The balloon catheter of claim 5 wherein theproximal and distal impregnated sections of the first layer are heatfusion bonded to the shaft.
 7. The balloon catheter of claim 5 whereinthe combined length of the proximal and distal impregnated sections offirst layer of the balloon is about 5 to about 50% of the length of thefirst layer.
 8. The balloon catheter of claim 4 wherein the length ofthe proximal impregnated section of first layer of the balloon is about1 to about 4 mm.
 9. The balloon catheter of claim 4 wherein the lengthof the proximal impregnated section of first layer of the balloon isabout 5 to about 20% of the length of the first layer.
 10. The ballooncatheter of claim 1 wherein the compatible polymeric materialimpregnated in the impregnated section of the first layer of the balloonis selected from the group consisting of polyamides, polyamide blockcopolymers, nylons, polyurethanes, polyurethane copolymers, andacrylonitrile butadiene styrene.
 11. The balloon catheter of claim 1wherein the compatible polymeric material impregnated in the impregnatedsection of the first layer of the balloon is soluble in alcohol.
 12. Theballoon catheter of claim 11 wherein the compatible polymeric materialimpregnated in the impregnated section of the first layer of the balloonis a thermoplastic polyamide.
 13. The balloon catheter of claim 1wherein the polymeric material of the shaft is selected from the groupconsisting of polyamides and polyurethanes.
 14. The balloon catheter ofclaim 1 wherein the impregnated section of the first layer of theballoon has a length less than a length of the section of the firstlayer which is not impregnated with the compatible polymeric material.15. The balloon catheter of claim 1 wherein the length of theimpregnated section of the first layer of the balloon secured to theshaft is about 1 to about 4 mm.
 16. The balloon catheter of claim 1wherein the compatible polymeric material impregnated in the impregnatedsection of the first layer of the balloon is the same polymeric materialas the shaft polymeric material.
 17. The balloon catheter of claim 1wherein the compatible polymeric material impregnated in the impregnatedsection of the first layer of the balloon and the polymeric material ofthe shaft are polyamides.
 18. The balloon catheter of claim 1 whereinthe compatible polymeric material impregnated in the impregnated sectionof the first layer of the balloon is different than said polymericmaterial of the shaft.
 19. The balloon catheter of claim 1 wherein theamount of the compatible polymeric material impregnated in the firstlayer of the balloon is about 1 to about 20% by weight of the firstlayer.
 20. The balloon catheter of claim 1 wherein the first layer ofthe balloon comprises expanded polytetrafluoroethylene.
 21. The ballooncatheter of claim 1 wherein the porous polymeric material of the firstlayer of the balloon is selected from the group consisting of expandedpolytetrafluoroethylene, expanded ultra high molecular weightpolyolefin, expanded ultra high molecular weight polyethylene, porouspolyethylene, porous polypropylene, and porous polyurethane.
 22. Theballoon catheter of claim 1 wherein the second layer of the balloon is anonporous layer comprising an elastomeric polymeric material.
 23. Theballoon catheter of claim 1 wherein the first and second layers of theballoon at the proximal and distal skirt sections are heat fusion bondedto the shaft.
 24. The balloon catheter of claim 1 wherein the section ofthe first layer which is not impregnated with the compatible polymericmaterial includes a central working length of the balloon having a stentmounted thereon for delivery and deployment of the stent.
 25. A ballooncatheter, comprising: a) an elongated shaft having a proximal end, adistal end, an inflation lumen, and at least a surface formed of apolymeric material; and b) a balloon on a distal shaft section, havingan interior in fluid communication with the inflation lumen of theshaft, and having a proximal and a distal skirt section bonded to theshaft, and a first and a second layer extending from the proximal skirtsection to the distal skirt section, the first layer having at least oneimpregnated section impregnated with a polymeric material which iscompatible with the polymeric material of the shaft and which isdifferent from a polymeric material forming the second layer of theballoon, the impregnated section being longitudinally adjacent to asection of the first layer which is not impregnated with the compatiblepolymeric material, and at least a portion of the impregnated sectionbeing fusion bonded to the shaft.